Articles: A or An? The or no article?

For beginners, click on this easy online exercise:

http://a4esl.org/q/h/9801/cg-a_an.html

If you want to learn or check some exceptions, click here:

http://www.eflnet.com/grammar/aan.php

http://www.usingenglish.com/quizzes/302.html

http://www.usingenglish.com/quizzes/21.html

htthttp://www.usingenglish.com/quizzes/216.html (Intermediate - with sentences)

Explanation:

http://owl.english.purdue.edu/owl/resource/540/01/

Have fun!